The present invention relates to a paperboard package of the parallelepiped configuration suitable for the consumer distribution of aseptically packaged liquid food products, and to an apparatus and associated method for producing scored blanks and packages made from such blanks.
The laminated paperboard parallelepiped package configuration is well established for marketing small consumer quantities of beverages and liquid foods. These packages are fabricated from a sheet material comprising a laminated composite having a paperboard substrate base and at least two layers of hot melt applied thermoplastic polymer such as polyethylene, PET or polypropylene, often with an interior metal foil layer such as aluminum. Packages of this construction typically are both gas and light impermeable. If assembled from sterile materials or materials that are sterilized after assembly and filled with sterile contents under sterile conditions, these packages, known as aseptic, are designed to insure that the contents may be safely consumed after storage for extended time periods without refrigeration.
Commercial sterility in the food packaging field is, therefore, that state or condition where a product, its package and associated filling and handling equipment are substantially free of harmful microorganisms capable of reproducing in the package confined food under normal, nonrefrigerated conditions of storage and distribution. Additionally, the product and its package are substantially free of viable microorganisms, including spores, of public health significance. Process conditions compatible with commercial sterility in low acid foods such as milk, cream, yogurt and vegetable juice include heating to the order of at least 140.degree. C. for at least 6 seconds. At the other end of the spectrum, high acid foods may require heating to only 93.degree. C. for about 15 seconds to achieve commercial sterility.
The paperboard substrate for these packages provides structural strength and rigidity to the composite and an excellent print surface for graphics. Consequently, a sealing layer of polymer is applied to the side of the paper to be used as the package interior and, while still hot and viscous, a layer of aluminum foil is applied onto the polymer film. The foil provides a sealing barrier against all gases and light. A second polymer layer most suitable for direct contact with the package contents is then applied over the foil.
In most cases, the base sheet lamination also receives a coating of polymer on the exterior surface of the paperboard applied over the graphics for external moisture protection of the paperboard, and scratch protection for previously applied graphics. Such a sequence is not exclusive, however, since there are marketing and production circumstances under which the graphics are applied over the exterior polymer coating. The base sheet lamination and fabrication processes referred to are normally practiced upon a continuously running sheet material drawn from a reel supply and rewound as a reel to become reel supply on another processing machine such as a printing machine. In the case of multiple color printing, each color in a complete composition may be applied at a separate print section. Register mechanisms along the sheet route through the machine regulate the running material position relative to each print station. The result is a repeating continuum of package blank graphics repetitively distributed along the reeled material length.
A folding score is typically applied in registry with the pattern of package graphics on the base sheet continuum of package blanks. Scores are channels or grooves pressed or embossed into the base sheet which delineate integrally adjacent panel areas of a package to be formed by folding a sheet of construction material. These scores facilitate folding and bending of the blank in erection of the container and therefore also delineate the boundaries of adjacent panel areas in the finished product.
Longitudinal score lines may be continuous or interrupted and oriented parallel with the web or base sheet running direction. This would also be parallel to the paper web machine direction (M.D.) which is the longitudinal or continuous running direction of the paper web as it was made. Such longitudinal score lines are typically embossed into a running web or laminated base sheet in the nip of a pair of scoring cylinders, one of which has a projecting ridge or ridges around its circumference and the other of which may be flat (anvil cylinder) or contain a groove around its (female cylinder) circumference which rotatably mates in spaced relation with the ridge on the male cylinder. As the web runs longitudinally through the cylinder nip, the male cylinder ridge and female or anvil cylinder pressingly engage the web therebetween to emboss a groove or score into the web.
Transverse or diagonal score lines of finite length may also be embossed between a pair of die cylinders in which a protruding ridge on a male cylinder meshes with a channel indentation on a female cylinder or is disposed in nip association with a co-rotating anvil cylinder.
Conventionally, all the protruding die ridge elements are positioned on one cylinder of a nip combination and any cooperative channels are positioned on the other cylinder. Generally, folded paperboard carton fabrication allows corner folds to be sharply turned over anvil cylinders or hard edges. In the case of aseptic, parallelepiped carton fabrication, however, the corners are typically not sharply broken or completed along any fold or score lines before the package is filled and sealed. Thus, the container may be filled as a rolled tube having its lateral edges sealed upon one another, often with a lapped closure and the leading end sealed in a similar manner. After the contents are inserted, the other end of the tube may be crimp or lap sealed to complete a fluid filled, flexible wall, pillow-like configuration. From this geometry, a parallelepiped shape may be formed by external shaping pressure surfaces to mold the pillow about the creased score lines. Resultantly, the package corners are generally softly rounded rather than crisp and sharp.
Due to the number and thickness of laminations required of aseptic package construction, effective scoring requires die nip pressure. Additionally, when the package closure folds are made, the corner pressures are compounded due to the doubling and redoubling of the sheet thickness about the fold line. As a consequence, the web preparation and packaging processes must be tightly controlled, and even slight deviations may result in rejection of packages due to foil or paperboard ruptures that occur during the folding or filling process.
It is, therefore, an object of the present invention to provide a parallelepiped package construction forming method and associated apparatus which imposes less compressive and tensile stresses on the package corners and edges.
Another object of the present invention is a method and associated apparatus for scoring package blanks which facilitates erection of the finally folded shape of the package according to the intended fold angle of adjacent panels so as to provide desired edge or corner characteristics.
A further object of the present invention is provision of a paperboard parallelepiped package having two opposite face surfaces and a linking end surface which are uninterrupted by seams or joints.
A further object of the invention is to provide a package blank, package configuration, and method and apparatus for making package blanks and packages from blanks which are relatively uncomplicated and convenient to make and use.